The present invention relates to a power steering apparatus for vehicles and a variable displacement pump for supplying a working fluid to the power steering apparatus.
Japanese Patent Application First Publication No. 2007-92761 discloses a variable displacement pump for use in a power steering apparatus for vehicles. The variable displacement pump of this conventional art includes a control valve for controlling an eccentric amount of a cam ring with respect to a central axis of a drive shaft (i.e., a pump element), and a solenoid for controlling an axial displacement amount of a valve body of the control valve. The variable displacement pump is constructed to control an amount of axial displacement of an armature of the solenoid by varying an amount of electric current to be supplied to the solenoid in accordance with an operating condition of the vehicle. As a result, the eccentric amount of the cam ring which is determined on the basis of an axial position of the valve body of the control valve is controlled, so that a discharge flow rate per one rotation of the pump (that is, a specific discharge amount of the pump) is varied.